There are numerous known methods for spraying molten material (mostly metals and polymers) to obtain particulate powders, such as spherical powders, having a defined size.
U.S. Pat. No. 2,997,245 discloses an apparatus for pulverizing and/or decomposing solid as well as molten materials. One embodiment of the apparatus comprises a crucible, which contains molten material, and is positioned above a system of annular resonator chambers resembling a Hartmann-Sprenger chamber. Compressed gas streams through an annulus against an edge belonging to a first annular resonator chamber, and then into a second annular resonator chamber. The arrangement of both resonator chambers generates supersonic, non-stationary shockwaves having ultrasonic frequency, which are then directed towards and focused on a small area of the material to be pulverized.
U.S. Pat. No. 4,485,834 discloses an apparatus for atomizing a molten material such as complex metal alloys, i.e., materials which are solid at room temperature. The apparatus utilizes an atomization die assembly which comprises a set of opposed linearly configured die elements which define a longitudinally configured die space or gap through which a sheet of molten material is discharged. The die elements have oppositely disposed orifice-bearing surfaces which form a nozzle assembly. An ultrasonic atomizing gas exits the linear array of orifices and impinges against a predetermined focal region of a sheet of molten material passing through the die space or gap. Each of the orifices have having resonating cavities associated therewith for generating ultrasonic high frequency shock waves for disintegrating the sheet of molten material at the focal region into fine particles. The ultrasonic shock waves generated exhibit frequencies of about 20 kHz to 30 kHz (primary), and at about 100 kHz (secondary).